Oxytocin Injection

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition

Issued and maintained by the United States Pharmacopeial Convention (USP)

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1 DEFINITION

Oxytocin Injection is a sterile solution of Oxytocin in a suitable diluent. Each milliliter of Oxytocin Injection possesses an oxytocic activity of NLT 90.0% and NMT 110.0% of that stated on the label in USP Oxytocin Units.

2 ASSAY

Procedure

Solution A: 0.1 M monobasic sodium phosphate

Solution B: Acetonitrile in water (1:1). Filter and degas before use. Make adjustments if necessary (see Chromatography 〈621〉, System Suitability).

Mobile phase: See Table 1.

Table 1

Diluent: Dissolve 5.0 g of Chlorobutanol in 5.0 mL of glacial acetic acid. Add 5.0 g of alcohol, 1.1 g of sodium acetate, and 1000 mL of water, and mix.

Standard solution: Dissolve the entire contents of a vial of USP Oxytocin RS in a known volume of Diluent. [Note - The solution may be diluted as necessary to a working concentration range for the Assay.]

Sample solution: Undiluted Oxytocin Injection. [Note—Allow NLT 25 min between injections.]

Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: UV 220 nm

Column: 4.6-mm × 12.0-cm; 5-μm packing L1

Column temperature: Room temperature

Flow rate: About 1.5 mL/min

Injection volume: About 100 μL

System suitability

Sample: Standard solution

[Note - Adjust the flow rate or the composition of the Mobile phase such that the retention time of oxytocin is approximately 10 min and between 15 and 17 min for chlorobutanol.]

Suitability requirements

Resolution: NLT 1.5 between oxytocin and the nearest adjacent peak

Relative standard deviation: NMT 2.0% for oxytocin from replicate injections

Analysis

Samples: Standard solution and Sample solution

Separately inject three equal volumes of the Standard solution and the Sample solution into the chromatograph allowing NLT 25 min between injections, and record the chromatograms as described in Chromatographic system. Identify the peaks, and determine the area of the oxytocin peak.

Calculate the percentage of the labeled amount of oxytocin in the portion of Oxytocin Injection taken:

Result = (r_U/r_S) × (C_S/C_U) × 100

r_U = mean values of the peak response of the Sample solution

r_S = mean values of the peak response of the Standard solution

C_S = concentration of USP Oxytocin Units/mL in the Standard solution (Units/mL)

C_U = label concentration of USP Oxytocin Units/mL in the Sample solution (Units/mL)

Acceptance criteria: 90.0%–110.0% of that stated on the label in USP Oxytocin Units

3 SPECIFIC TESTS

Bacterial Endotoxins Test 〈85〉: It contains NMT 35.7 Endotoxin Units/USP Oxytocin Unit.

pH 〈791〉: 3.0–5.0

Particulate Matter in Injections 〈788〉: Meets the requirements for small-volume injections

Injections and Implanted Drug Products 〈1〉: Meets the requirements

4 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in single-dose or multiple-dose containers, preferably of Type I glass, or in suitable plastic containers.

Labeling: Label it to indicate its oxytocic activity in USP Oxytocin Units/mL. Label it also to state the animal source if naturally derived, or to state that it is synthetic.

USP Reference Standards 〈11〉

USP Oxytocin RS